ASSESSMENT OF THE DIABATIC HEATING DISTRIBUTION AND GLOBAL TELECONNECTION ERRORS IN THE UKMO UNIFIED MODEL DURING ENSO

Interannual variability in tropical sea surface temperatures (SSTs) is able to influence the atmospheric circulation in more remote regions. This is achieved due to a succession of processes, beginning with the generation of convection anomalies through to the impact of global teleconnection patterns. The major source of interannual variability in tropical SSTs is due to ENSO. AMIP II integrations using the UKMO Unified Model (UM) (version HadAM3) reveal that the global response during ENSO conditions is exaggerated compared to observations. Analyses of these integrations are performed in order to determine the major sources of error in the model. In particular, the ability of the model to reproduce the correct magnitude and spatial distribution of the tropical diabatic heating anomalies in response to ENSO sea surface temperature (SST) distributions will be discussed. ENSO also influences the more remote tropical climate through known global teleconnection patterns. In the tropics a remote response to ENSO is observed in the tropical Atlantic, primarily through changes in the Walker circulation. During El Nino conditions, increased descent is seen over the tropical Atlantic tending to result in a warming of SSTs. The intensity of this response gives rise to stronger than observed coupling between tropical Pacific and tropical Atlantic SSTs. The impact of vertical resolution on model skill will also be assessed, with a comparison of 19 level and 58 level versions of the AMIP II UM integrations.